Group-Admin Escalation to Realm-Admin

Summary

A flaw was found in Keycloak. A missing authorization check in the GroupResource.addChild() endpoint within the Admin REST API allows an authenticated user with limited administrative privileges to reparent any existing group. When Fine-Grained Admin Permissions v2 (FGAPv2) is enabled, an attacker with management rights over a single low-privilege group can reparent a highly privileged group (such as one possessing the realm-admin role) under their managed group. Because group permissions follow a hierarchical structure, this action unauthorizedly grants the attacker management and password-reset capabilities over the members of the targeted privileged group. An attacker can exploit this to reset an administrator's password, compromise the account, and achieve a full realm takeover, leading to a complete compromise of confidentiality, integrity, and availability. A flaw was found in Keycloak. A missing authorization check in the GroupResource.addChild() endpoint within the Admin REST API allows an authenticated user with limited administrative privileges to reparent any existing group. When Fine-Grained Admin Permissions v2 (FGAPv2) is enabled, an attacker with management rights over a single low-privilege group can reparent a highly privileged group (such as one possessing the realm-admin role) under their managed group. Because group permissions follow a hierarchical structure, this action unauthorizedly grants the attacker management and password-reset capabilities over the members of the targeted privileged group. An attacker can exploit this to reset an administrator's password, compromise the account, and achieve a full realm takeover, leading to a complete compromise of confidentiality, integrity, and availability. This vulnerability is rated as High impact. When Fine-Grained Admin Permissions (FGAPv2) are enabled in Keycloak, a delegated administrator with specific `manage-members` permissions on a low-privilege group can bypass authorization checks to reparent any other group, including those with `realm-admin` roles. This allows the attacker to reset passwords of members in the stolen group, leading to a full realm takeover. Red Hat severity: Important — CVSS 7.7 (CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:N). Weakness: CWE-639. Fixed by RHSA-2026:30050, RHSA-2026:30049, RHSA-2026:30084, RHSA-2026:30083 — update the affected packages (`sudo dnf update`). Affected Red Hat products: Red Hat build of Keycloak 26.4; Red Hat build of Keycloak 26.4.13; Red Hat build of Keycloak 26.6; Red Hat build of Keycloak 26.6.4.